The present invention relates to stabilizing jacks for recreational vehicles adapted to raise the recreational vehicle relative to its suspension to provide stability to the vehicle when parked.
A wide variety of stabilizing jacks have been developed for use in stabilizing recreational vehicles, trailers and the like when parked by raising the vehicle relative to its suspension system to prevent rocking and swaying of the recreational vehicle as an occupant moves around in the vehicle. For example, U.S. Pat. No. 4,103,869 discloses a stabilizing system utilizing four separate jacks mounted in the corners of the vehicle with each jack having a separate gearmotor for extending and retracting the leg of the jack. Raising and lowering of the jacks is controlled by an electronic switching system to selectively raise and lower one jack at a time to stabilize and level the vehicle.
Although stabilizing systems such as that shown in U.S. Pat. No. 4,103,869 do conveniently allow the user to raise and lower all four jacks from one location, the need for a separate motor for each jack leg significantly increases the cost of the stabilizing system. In addition, raising and lowering each jack leg independently makes it difficult to properly stabilize the vehicle. For example, with the leg of one of the rear jacks lowered into contact with the ground, as the leg of the other rear jack is lowered into contact with the ground to the point that it pushes upward on the vehicle body, it also lifts the opposite jack leg slightly off of the ground. Using such a system it is difficult to ever get all four jack legs touching the ground at the same time to provide the desired stability.
U.S. Pat. No. 3,870,276 discloses a stabilizing jack for recreational vehicles having a pair of jack legs which are raised and lowered using a single motor. The jack legs are mounted on a frame such that the legs are simultaneously moved downwardly into a stabilizing position beneath the vehicle with an equal force on both of the legs and such that both of the legs strike the ground before further force is applied to either leg to raise the vehicle, such as when the stabilizer is extended on uneven terrain. However, the usefulness of the stabilizing jack as shown in U.S. Pat. No. 3,870,276 is severely limited because the motor for each set of legs is mounted so as to extend downward from the vehicle. In this position, the motor and the stabilizing jack system are prone to damage during transport of the recreational vehicle because of clearance problems. In addition the configuration of the ""276 patent limits the length of the legs such that the system may not be useable with current style coaches or trailers whose frames tend to sit higher off of the ground. The newer generation coaches sit higher off of the ground to accommodate slide out rooms and the like.
There remains a need for a relatively low cost stabilizing system which facilitates stabilizing of recreational vehicles and which may be driven by a motor.
The present invention comprises a stabilizing jack for vehicles having a pair of jack legs advanceable between retracted and extended or raised and lowered positions by a single drive assembly, wherein the drive assembly is mounted on a slide frame which is slidably mounted to a base frame. The base frame is securable to the frame of a vehicle such as a recreational vehicle to stabilize the vehicle when parked.
When the legs are lowered on uneven ground, one leg will engage the ground before the other preventing that leg from further downward advancement but causing the drive assembly to drive the slide frame in an opposite direction while the other leg continues to advance downward until it engages the ground. Once both legs engage the ground, the balanced forces acting through the legs prevents the slide frame from sliding relative to the base frame such that the legs push downward on the ground with equal pressure, pushing upward on the mounting frame and raising the vehicle.
In a preferred embodiment, the drive assembly comprises a drive screw having adjacent left and right hand threaded sections with a screw follower or trunnion secured to each threaded section. Each leg is pivotally secured at a first end thereof to one of the screw followers. Struts or leg braces are pivotally connected at one end to each leg, medially thereof, and are pivotally connected at opposite ends to the base frame at the ends closest the respective leg.
When the screw followers are positioned centrally relative to the drive screw or in close proximity to the transition between the left and right hand threaded sections, the legs are positioned in a retracted position relative to the slide frame and base frame. When the screw is rotated in a first direction, the screw followers advance outward relative to the screw, causing the legs to pivot downward or toward an extended position. When the screw is rotated in an opposite direction, the screw followers advance inward relative to the screw, causing the legs to pivot upward or toward the retracted position.
As the screw is rotated in the first direction and one leg engages the ground before the other, the engagement of that leg against the ground resists outward advancement of the screw follower attached to the leg at its upper end thereof relative to the ground, such that the screw and the slide frame advance in the opposite direction relative to the ground until the other leg touches the ground. Once both legs touch the ground, the equal and opposite forces acting on the slide frame generally prevent it from sliding relative to the base frame and the screw followers are forced outward against the resistance thereon, causing the base frame to push upward on the vehicle raising it relative to its suspension system.
The drive screw is preferably driven by a motor connected to the drive screw at one end thereof The motor is adapted to automatically shut off when the load thereon exceeds a selected amount, which occurs when the vehicle is raised sufficiently to stabilize the vehicle.